The present invention relates to semiconductor processing and, more particularly, improved CMP uniformity.
In semiconductor processing, it is desirable to produce a uniform planar surface for subsequent processing such as, for example, lithography. Typically, a chemical mechanical polish (CMP) is employed to produce a planar surface on the substrate.
Generally, CMP systems hold a thin flat wafer of semiconductor material in contact, under a controlled downward pressure, with a polishing pad that moves relative to the semiconductor wafer. The semiconductor wafer may be stationary or it may also rotate on a carrier that holds the wafer. A backing film is optionally positioned between the wafer carrier and the wafer. The polishing platen is typically covered with a relatively soft wetted pad material such as blown polyurethane.
A liquid compound or slurry is often provided between the semiconductor wafer and the polishing pad to facilitate polishing of the wafer. The slurry serves to lubricate the moving interface between the semiconductor wafer and the polishing pad while mildly abrading and polishing the semiconductor wafer surface. Typical slurries comprise, for example, silica or alumina in a solution.
Due to normal usage, the surface of the pad becomes uneven. The non-uniform surface of the pad causes a non-uniform polish, resulting in a relatively uneven substrate surface. A non-uniform substrate surface is undesirable as it adversely affects subsequent processes, decreasing manufacturing yields. Typically, to combat the adverse affects of a non-uniform pad, it is periodically conditioned to smooth its surface. However, even with periodic conditioning of the pads, non-uniformities in the substrate surface after CMP still occurs.
In view of the foregoing, improve CMP uniformity is desirable to improve manufacturing yield.
The invention relates to semiconductor manufacturing and, in particular, to improved polishing of wafers. In one embodiment, the invention improves the control of the slurry distribution during polishing. The improved control of the slurry distribution is achieved by providing a slurry dispenser which dispenses slurry onto the pad from a plurality of positions or locations. In one embodiment, the slurry is dispensed from a plurality of radial positions of the polishing pad. In another embodiment, the slurry is dispensed from a plurality of angular positions of the polishing pad. In yet another embodiment, the slurry is dispensed from a plurality of radial and angular positions of the pad. The radial and angular positions in which the slurry is dispensed can be varied or adjusted over time to account for changing conditions.
In another embodiment, a squeeze bar is provided in the path between the slurry and substrate. The squeeze bar is used to shape the slurry distribution. The squeeze bar can have a plurality of positions between the slurry dispenser and substrate to produce the desired slurry distribution. The squeeze bar can be provided with additional parameters to improve the control of the slurry distribution.